1. Field of the Invention
The present invention relates to a device for transmitting and receiving.
The invention falls within the field of data transmission. Although it can be used in principle in any digital communication system for bidirectional data transmission, the present invention and its underlying problem will be explained below with reference to a “ZigBee” communication system in accordance with IEEE 802.15.4.
2. Description of the Background Art
So-called “Wireless Personal Area Networks” (WPANs) can be used for the wireless transmission of information over relatively short distances (about 10 m). In contrast to “Wireless Local Area Networks” (WLANs), WPANs require little or even no infrastructure for data transmission, so that small, simple, power-efficient, and cost-effective devices can be implemented for a broad range of applications.
The standard IEEE 802.15.4 specifies low-rate WPANs, which are suitable with raw data rates up to 250 kbits/s and stationary or mobile devices for applications in industrial monitoring and control, in sensor networks, in automation, in the field of computer peripherals, and for interactive games. In addition to a very simple and cost-effective implementability of the devices, an extremely low power requirement of the device is of critical importance for such applications. Thus, an objective of this standard is a battery life of several months to several years.
Known transmitting/receiving devices comprise a transmitting/receiving unit for transmitting and receiving data according to a communication standard and a control unit for controlling the transmitting/receiving unit, so that the power requirement of the entire transmitting/receiving device results from that of the transmitting/receiving unit plus that of the control unit.
Typically, the transmitting/receiving unit senses the functionalities specified at the level of the physical layer (PHY) of the communication standard, whereas the control unit assumes those of the MAC layer and optionally higher layers. The PHY functionalities hereby include, for example, the transmitting and receiving of PHY data frames (PPDU) over the physical channel (modulation/demodulation, synchronization, etc.) and the checking of channel occupation (clear channel assessment, CCA). Methods for increasing the robustness of the data transmission, such as, e.g., the acknowledgment of successfully received PHY data frames by acknowledgement frames (ACK), the further procedure in abortive transmission attempts, or anti-collision methods such as CSMA-CA (carrier sense multiple access with collision avoidance), in contrast, are specified at the MAC level.
Due to the resulting temporary activities and different operating modes with a different operating power requirement, the power requirement of the transmitting/receiving unit and/or the control unit is not constant over time but varies considerably. It is a disadvantage hereby that in some of the time segments, in which, e.g., the transmitting/receiving unit has an increased power requirement, the control unit also requires a large amount of operating power. Conversely, it cannot be ruled out that the transmitting/receiving unit requires a large amount of power, when the control unit also has an increased demand. The entire transmitting/receiving device therefore has a power requirement with high peak values (peaks). The peak currents resulting from this increase not only the average power requirement of the transmitting/receiving device, but disadvantageously may require larger dimensioning of the power supply unit (battery).